A. Field of the Invention
This invention relates to a sensor for checking value documents and to a method for manufacturing the sensor from a sensor platform, as well as to a sensor family having at least two sensors manufactured from the same sensor platform.
B. Related Art
For checking value documents there are usually employed sensors with which the type of the value documents is determined and/or with which the value documents are checked for authenticity and/or for their state. Such sensors are employed for checking value documents such as e.g. bank notes, checks, identity cards, credit cards, check cards, tickets, vouchers and the like. The check of the value documents is effected in an apparatus for value-document processing, in which one or several different sensors are contained, depending on the value-document properties to be checked. Upon checking, the value documents are usually scanned in one or several tracks, whereby the sensor and the value document are moved relative to each other.
The value documents are frequently checked using optical sensors that capture the light reflected by the value documents. Previous optical sensors have been restricted to the spectral properties of the sensor that are defined upon the development of the sensor, such as e.g. the spectral resolution and the position and width of the spectral region capturable by the sensor. To adapt such an optical sensor to different requirements, e.g. a different spectral region or a different spectral resolution, basic changes of the optical components of the sensor are required. With optical sensors whose spectral selection is effected through different color filters which are respectively arranged in front of a detector, it would e.g. be necessary to replace the color filters to change the capturable spectral region. To increase the spectral resolution in such a sensor, additional detectors with different color filters would have to be installed in the sensor. This is usually hardly possible, however, on account of the limited space within the sensor housing.
It is also known to illuminate a value document by employing several different-colored light sources whose light is directed onto the value document via a common light guide. On account of the relative motion between the sensor and the value document transported past it, however, a minimum distance is required between the light guide and the sensor. Because the light diverges after exiting from the light guide, this minimum distance results in the illuminated region on the value document being relatively large and the illumination intensity accordingly low. Hence, such an illumination is unfavorable when the optical properties of a value document are to be captured in a spatially limited region.